1. Field of the Invention
The invention relates to the field of communication. More specifically, the invention relates to communication networks.
2. Background of the Invention
Current networks must satisfy consumer demand for more bandwidth and a convergence of voice and data traffic. The increased demand of bandwidth by consumers combines with improved high bandwidth capacity of core networks to make edge networks a bottleneck despite the capacity of optical networks.
Multiplexing is used to deliver a variety of traffic over a single high speed broadband line. An optical standard such as Synchronous Optical Network (SONET) or Synchronous Digital Hierarchy (SDH) in conjunction with a multiplexing scheme is used to deliver various rates of traffic over a single high speed optical fiber. SONET/SDH is a transmission standard for optical networks which corresponds to the physical layer of the open standards institutes (OSI) network model. One of the protection schemes for SONET/SDH involves automatic protection switching (APS) in a bi-directional line switched ring (BLSR) architecture. BLSR utilizes linear switching to implement APS.
High speed optical rings offer large amounts of bandwidth, but the protection scheme utilizes 50% of that bandwidth. This 50% of total bandwidth for a protection channel typically goes unused while there is not a failure. It is typically unused because traffic transmitted in the protection channel would be preempted by the working TDM traffic when a failure occurs.
An alternative to unprotected preemptable traffic in a protection channel is to provide a non-preemptable unprotected traffic (NUT) channel. A NUT channel allows for an implementation that runs a unidirectional path switched ring (UPSR) over a BLSR. Unfortunately, the traffic carried in a NUT channel may be dropped if a failure occurs in the BLSR. Hence, certain customers will not purchase NUT channels.